Rotorcraft drive systems can include various components that produce and transfer power. For example, engines and gearboxes are standard components. Such components generate heat and require lubrication. Excessive levels of heat can cause premature failure and create safety risks. Proper lubrication serves to reduce heat generation and assist in heat removal from moving components within gearboxes.
Typically, rotorcraft use a variety of primary lubrication systems to provide wear protection and heat transfer for moving components. Under normal operating conditions, primary lubrication systems provide proper lubrication and heat removal. However, primary lubrication systems can fail to result in excessive heat generation, wear, and failure of components, such as bearings or gears within a gearbox.
Rotorcraft are generally required to maintain manageable flight operations for selected durations of time if the primary lubrication system fails. One method used to satisfy the requirements of manageable flight during a lubrication system failure is to use a secondary, emergency lubrication system to operate when the primary lubrication system fails. This method increases the overall weight of the rotorcraft. Therefore, an improved method of controlling heat transfer from an aircraft gearbox is desired.